from abc import ABC, abstractmethod

class QuackBehavior(ABC):
    @abstractmethod
    def quack(self):
        pass

class Quack(QuackBehavior):
    def quack(self) -> None:
        print("Quack")

class Square(QuackBehavior):
    def quack(self) -> None:
        print("Squack")

class MuteQuack(QuackBehavior):
    def quack(self) -> None:
        print("<<Silence>>")